A version of the finite element method for frictional contact problems

We propose a method for solving frictional contact problems which is based on including the generalized coordinates of absolutely rigid bodies in the degrees of freedom of the system under study and on varying the functional of the variational problem with respect to these coordinates. As a result, one can include the generalized coordinates or the energy-conjugate generalized forces directly in the right-hand side of the resolving system of equations, which permits easily taking into account any laws of motion or loading of absolutely rigid bodies.     

Nonequivalence of NH Bonds in the Amino Group of Aminotoluenes in Complexes of Various Compositions

The association of aminotoluenes with different proton acceptors in CCl₄ was studied in the temperature range 290–330 K on the basis of IR absorption spectra in the region of the amino group stretching vibrations. It is found that the location of the maximum, halfwidth, and integrated intensity of the absorption bands (NH) of monomers and H-bonded complexes depend almost linearly on temperature. It is shown that in the 1:1 complexes the hydrogen bonding is more stable than in the 1:2 complexes.     

A Spectroscopic Study of Thermodynamic Characteristics of Hydrogen-Bond Complexes of Dichloroanilines with Proton Acceptors

The association of dichloroanilines with different proton acceptors in CCl₄ in the temperature range 290–330 K is studied using the IR absorption spectra in the region of stretching vibrations of an amino group. It is found that the position of maximum, halfwidth, and integral intensity of the (NH) absorbtion bands of free and H-bond molecules change almost linearly within the temperature range studied. The temperature dependence of constants of the equilibrium monomer – complex is examined, and thermodynamic characteristics of the complexes are calculated.     

Dynamic, electrooptical and energetic nonequivalency of NH bonds in 1:1 and 1:2 complexes of aminopyridines with proton acceptors

The influence of the –NH₂ group position in the pyridine ring on the proton donor ability of N–H groups in hydrogen bonding as well as on the spectral behaviour of stretching and bending vibrations of aminopyridines has been studied. The proton donor ability was shown to increase in the row: meta-, ortho-, and para-aminopyridines. It was established tha N–H bonds in ortho-aminopyridine were not equivalent, and the evaluation of their dynamic nonequivalence was made.

The influence of temperature on the spectral characteristics of the absorption bands of the stretching vibrations of amine groups in the free and hydrogen bonded molecules in CCl₄ has been studied (in temperature range 290–330 K), the formation constants of the complexes have been determined, enthalpy of the 1:1 complexes formation (−ΔH₁) between ortho- and meta-aminopyridines with dimethylformamide, dimethylsulphoxide and hexamethylphosphoramide has been calculated in temperature range 290–330 K. The 1:2 complexes of ortho-, meta- and para-aminopyridines with acetonitrile, tetrahydrofurane, dimethylsulphoxide, hexamethylphosphoramide were studied at the indoor temperature. Enthalpy of the 1:2 complex (−ΔH₂) was estimated on the basis of ‘intensity rule’; −ΔH₁=ΔB^1/2 assuming that parameter does not depend on the composition of a complex.

The vibrational and electrooptical tasks were solved for the free and H-bounded molecules of aminopyridines as well as its complexes of the 1:1 and 1:2 compositions. Dynamic, electrooptical and energetic nonequivalency of NH bonds of aminogroups in aminopyridines was studied quantitatively. The independent calculations of dynamic constants proved mentioned above nonequivalency of NH bonds.

Correlations between spectral characteristics of the absorption bands, geometric, dynamic and electrooptical parameters of –NH₂ group in aminopyridines in the free and hydrogen bonded molecules have been established. Those correlations allow to determine the most important molecular characteristics obtained on the basis of spectral measurements in the range of the absorption bands of the stretching vibrations of aminogroup.     

Quantum-Chemical Investigations of the Photolysis of Monochloro-Substituted Aniline Molecules

Russian Physics Journal -     

Dynamic and Electro-Optical Nonequivalence of the NH Bonds of the Amino Group in Complexes of Dichloro-Substituted Anilines

The IR spectra of 1:1 and 1:2 complexes of dichloro-substituted anilines with various proton acceptors have been investigated and the parameters of the absorption bands of the stretching and deformation vibrations of their amino group have been determined. Vibrational and electro-optical problems have been solved for free and H-bonded molecules of the studied amines within the framework of the R-NH₂ model of a valence-free field. The geometric, dynamic, and electro-optical parameters of the amino group of dichloro-substituted anilines in complexes of different compositions have been determined. It is shown that the hydrogen bond in 1:1 complexes appears to be stronger than in 1:2 complexes.     

Investigation of the Heavy-Atom Effect on the Spectral-Luminescent Properties of Dichloroanilines

The influence of the chlorine atom position on the spectral, geometric, and photophysical characteristics of free molecules of dichloroaniline is studied by electron spectroscopy, fluorescence, and quantum chemistry. A chlorine atom included in the aniline aromatic ring is shown to exhibit properties inherent in a heavy atom, that is, the radiation is dominated by phosphorescence. According to quantum-chemical calculations, the quenching of fluorescence is due to the fact that the efficiency of the intersystem crossing conversion proves to be much higher than the radiative decay rate of the S ₁ state.     

Quantum-Chemical Investigation of Spectral-Luminescent and Physical-Chemical Properties of Benzamides

The effect of a halogen atom in orthoposition of a phenyl radical on the spectral, geometrical, and photophysical characteristics as well as on the proton-donor and proton-acceptor properties of the 2-Cl- and 2-Br-benzamides was studied by electron spectroscopy and quantum chemistry. The intersystem crossing is shown to be the major decay pathway for lower singlet states. A comparative analysis of the bond populations of free molecules of benzamide and its halogen derivatives suggests that NH bonds of an amino group are nonequivalent in the amides under study.